As most people know, practically every boxer has his favorite punch or blow.
Mr. Boardman, in his interview, touches on head blows alone.
A "knockout punch" is one that renders the receiver unable to face his opponent for no less than 10 seconds. It is a blow landed to some vulnerable spot on the anatomy.
The most common knockout blow, and the best known, is the "hook to the jow" punch. Few clean knockout blows reach the extreme tip of the chin, as it is a hard blow to land, because of the natural protection of the hands and arms, and the keeping of the chin well down on the chest.

The left hook to the side of the jaw is the most common knockout blow.

It is usually delivered at close range, being out of the line of the vision, and making it harder to guard off.
The line of drive is made so as to force the upper end of the jawbone, ball, and socket up into the brain area, near where it is fastened to the upper skull.

On coming to, he usually hears a low, buzzing, and steaming noise, and faint sounds of the referee, or crowd. '
This knockout blow also sometimes disturbs the fluid in the semi-circular canals of the ear, where the sense of equilibrium is located, causing a loss of balance.

Sometimes old-time fighters habitually walk with a wobble, or sense of unbalance, caused by being beaten over the ear so as to partially destroy the sense of the balance fluid.

The most deadly effect is obtained when the blow is delivered and the jaw is not tense, especially when the fighter is tired or when the mouth is partially open. Many fighters wear patent mouth pieces, or mouth-guards, so that the teeth may be clenched, and thereby take away any shock. A tightening of the jaw makes the blow much less effective.

the caratoid artery, or neck blow, is the most sensational and least painful of blows. The punch lands on the upper side of the neck under the ear and just below the jaw, where the main external artery divides — one part supplying the brain, the eyes, and ears, and the other part supply the face, tongue, and internal parts.

This blow is reflectory, and sometimes induces a sympathetic action of the vagus nerve, causing a temporary inaction of the heart and breathing organs, thus bringing about senselessness.

It is also very effective when the neck muscles are relaxed.

The mastoid is located directly behind the ear, encasing the ear bones, and is the hardest bone in the body. The blow is landed directly behind or over the back part of the ear. It does not always produce a knock-out, but shocks the brain and causes the victim to stagger and wobble for a few seconds. Many boxers shows its effect by "cauliflower" or clipped ears.

The temple is located directly in front of the ear, and just above the upper jawbone. It is the thinnest part of the skull. The temple blow is the most dangerous of all, and may have a fatal effect.

The "rabbit punch" is delivered directly at the base of the skull or back of the head. It is usually delivered when a man ducks or weaves too much, and is in a bent-over position.

It shocks the brain, sometimes produces partial paralysis of the breathing functions, and causes a concussion or shock.
It is crude, unsportsmanlike, and scientific, and is regarded as a foul in practically all parts of the world.